Fig. 1. Schematic of the circular aperture at the edge of the segmented mirror

Fig. 2. Theoretical diffraction pattern with piston error changing from -λ/4 to λ/4

Fig. 3. Cross-correlation curve of diffraction spot with piston of 0.11λ and template pattern

Fig. 4. The aperture of the micro-lens deviates from the center of the segment edge in the X direction

Fig. 5. Different alignment errors lead to piston error

Fig. 6. Cross-correlation curves of PSF and template when tip，tilt errors are 0.1″

Fig. 7. Optical detection scheme of the two-segmented mirror system

Fig. 8. Schematic diagram of the optical device arrangement of the two-segmented mirror system

Fig. 9. Piston generated by actuator displacement，piston measured by PSF cross-correlation detection method，and edge sensor readings

Fig. 10. The residuals of the measured values of the piston and PSF cross-correlation method and the measured values of the edge sensor generated by the displacement of the actuator

Fig. 11. 4D interferometer measurement results

Fig. 12. In closed-loop control，the change of the detected value of the PSF cross-correlation detection method and the change of the measured value of the edge sensor